The present invention relates to the production of hydrocarbon fluids from a reservoir. More particularly, the present invention relates to a production well analysis and management system that can be operated from the well surface.
The recovery of hydrocarbon fluids such as oil and gas from a subsurface reservoir or well requires downhole production equipment to control the hydrocarbon fluid flow. This production equipment typically includes tubing to convey the fluids from the geologic formation to the well surface, packers to isolate discrete hydrocarbon producing zones, and other tools to monitor and control fluid flow from the producing zones.
Well production operations are complicated by variables such as multiple producing zones having different fluid chemical compositions, fluid migration from one producing zone to another, differing temperatures and formation pressures, and the variable performance of each producing zone over time. These variables significantly influence the management of a well and further affect the ultimate recoverability of hydrocarbons from the well. Existing production well control systems do not efficiently monitor and control these variables in a multiple zone well.
Production well control systems are encumbered by the direct and indirect costs of obtaining production fluid data, by the uncertainty in predicting reservoir response to modified tool parameters, by the direct and indirect cost of well interventions, and by the risk and uncertainty associated with mechanical interventions. Certain existing intervention techniques irrevocably affect reservoir production and do not permit the return of the reservoir or well equipment to the original state.
At present, downhole well conditions are typically monitored by a single guage installed in a side pocket mandrel above the production packer. The data is communicated to the well surface with an electric conductor. The guage can measure fluid pressure and temperature and is retrievable to the well surface with a wireline. Such guages provide limited information regarding the production parameters of the entire well because the guages do not measure the temperature and formation fluid pressure at each discrete interval in a multiple zone well.
In addition to the need for information regarding well conditions, a need exists for systems to operate production equipment. Hydraulic lines providing hydraulic power have been used to remotely control certain downhole devices such as safety valves. Such valves are held in an open position when the hydraulic line is pressurized, and are closed by a spring driven actuator when the pressure in the hydraulic line is reduced. To increase the reliability of a safety valve, a redundant hydraulic line can be engaged with a second actuator to close the valve if the primary system fails. This redundancy increases the reliability of the operating system but does not increase the actual reliability of the safety valve.
If a safety valve is located at a relatively shallow depth in a vertical well, the probability of hydraulic line damage is slight. However the probability of hydraulic line damage increases at greater depths and in horizontal wells. In deep vertical wells, potentially destructive contact between the hydraulic lines and the wellbore is increased during installation of the production well tools. In horizontal wells, the production tubing and attached hydraulic lines rest against the lower side of the borehole and can be damaged. Such hydraulic lines cannot be efficiently secured to the upper side of the production tubing because the production tubing often twists in a helical fashion during tubing installation.
If the hydraulic line redundancy in subsurface safety valves was adapted to a horizontal well section, multiple hydraulic lines and actuators would be required for each tool. In a tool string with five downhole tools, five discrete hydraulic lines would be required to provide primary tool control, and ten discrete hydraulic lines would be required to provide primary and redundant power for each tool. This configuration is unwieldly and would complicate installation and control of well production equipment.
Although electric lines could theoretically control the operation of downhole well tools, such electric lines cannot carry sufficient current to operate certain downhole tools. To provide the requisite power, large and cumbersome electric conductors would complicate the design and operation of a multiple tool well production system. Additionally, electric conductors in horizontal wells would be exposed to the destructive forces caused by the tubing as it rests against the lower part of the wellbore.
Accordingly, a need exists for a well control system that permits the remote control of well production tools. The well control system should provide for cyclical control of the well tools and should provide reliable operation of the well tools in adverse environments such as horizontal and deep vertical wells.